Method and apparatus for determining the time curve of the intensity of radiation in a weathering testing device

ABSTRACT

A method for determining the time curve of the intensity of radiation present at the location of at least one sample which is being examined. The sample follows a circular path of movement in a sealed sample chamber of a weathering testing device, around a stationary radiation device for producing UW and global radiation. At least one sensor which detects the momentary radiation intensity of the radiation device is provided. The sensor moves together with the at least one sample, and is displaced in relation thereto in relation to the radiation device, for example in the peripheral direction of the path of movement. An electrical signal corresponding to the momentary intensity of the radiation is derived by the sensor at set intervals.

FIELD OF THE INVENTION

The invention relates to a method for determining the course over timeof the radiation intensity at the location of at least one sample to beexamined, which moves in an enclosed sample chamber of a weatheringtesting device over a circular path of motion about a stationaryradiation device for generating UV and global radiation, having at leastone sensor detecting the instantaneous radiation intensity of theradiation device, which sensor, together with the at least one sampleand offset from it relative to the radiation device, for example offsetin the circumferential direction of the path of motion, movessubstantially along the path of motion, and an electrical measurementsignal corresponding to the instantaneous radiation intensity is derivedby the sensor at intervals over time. The invention also relates to adevice used to perform this method.

BACKGROUND OF THE INVENTION

Weathering testing devices are used to test the lightfastness and agingof arbitrary samples, which are distributed over a circular path ofmotion in the enclosed sample chamber and move around the stationaryradiation device. Rain bars or other stationary equipment elements canalso be provided in the weathering testing device to allow examinationof specimens taking the required ambient conditions into account. As aresult, the radiation path from the radiation device to the samples andto the sensor moved along with the samples is repeatedly interrupted orinterfered with by stationary obstacles presented by the equipment. Inthe known devices, the course over time of the radiation intensity isascertained by making practically individual snapshots of the radiationintensity at comparatively long time intervals or at isolatedcircumferential positions along the path of motion. It is accordinglyimpossible to estimate how the equipment-dictated unavoidableinterruptions of radiation will affect the measurement error indetecting the radiation intensity. Accordingly it is certainly possiblethat the radiation interruptions will repeatedly arrive at unfavorablerotational positions of the sensor around the radiation device, causingconsiderable measurement error with regard to the radiation sent to thesamples.

SUMMARY OF THE INVENTION

The object of the present invention is to embody a method and a deviceof the generic type in question such that while avoiding the abovedisadvantages, more-reliable detection of the course over time of theradiation intensity at the location of the sample is possible.Individual stationary obstacles presented by the equipment to theradiation should have practically no further effect of adulterating theoutcome. The method should also be well-suited to industrial realizationusing current- or energy-saving circuit components, such as for batteryand rechargeable battery operation of a device functioning accordingly.

For attaining this object, the measurement signal is integrated inanalog fashion in accordance with a first, adjustable timing code withrelatively short code intervals at least once in each of these shortcode intervals via a certain integration interval of adjustablechronological length; that the thus-obtained analog-integratedmeasurement values of each short code interval are digitized; that thedigitized measurement values of a plurality of successive code intervalsof the first timing code are arithmetically added and averaged inaccordance with a second, adjustable timing code with comparativelylonger code intervals, in each of these longer code intervals; and thatthe thus-obtained arithmetically added, averaged measurement values arestored in memory digitally in a manner capable of chronologicalassociation and capable of being called up.

In this method, the influence of individual stationary obstacles toradiation presented by the equipment on the outcome of measurement ispractically precluded, since in the analog integration operations,repeated at rapid time intervals, with chronologically long-lastingintegration intervals and ensuing addition and averaging of a pluralityof individual outcomes, instantaneous situations unfavorable from aradiation standpoint are dropped from the outcome or practically fail toarise. Because of the relatively brief integration intervals withensuing digitization and digital further processing and storage inmemory, the method is very well-suited for a relatively simple,inexpensive practical embodiment, such as for battery and rechargeablebattery operation, and thus for mobile use of suitably operating devicesusing economical circuit components available on the market.Furthermore, for non- battery operation, the influence of possiblefluctuations or breakdowns in mains voltage on the outcome ofmeasurement is largely suppressed.

Only the arithmetically added and averaged measurement values are storedin memory for longer, the course over time of the radiation intensitycan also be detected over a longer period of time without major expensefor memory.

The particularly randomly controlled shifting of the integrationintervals lead to a further improvement in the reliability of themethod, since the influence of existing interference variables that havethe same effect and are thus added together is avoided even more. Thisis true both for the influence of obstacles to radiation and theinfluence of mains disruptions.

To attain the stated object, a device suitable for performing themethod, is distinguished according to the invention by connecting to theoutput of the sensor 20, 22 a clocked analog integrator 26, which inanalog fashion integrates the measurement signal, in accordance with afirst, adjustable timing code with relatively short code intervals a atleast once in each of these short code intervals, via a certainintegration interval c of adjustable chronological length; displaydevice 34. A microprocessor 36 controls the individual components of thedevice and can, as in the present case, be linked with an randomgenerator 38.

This device, with a comparatively simple and inexpensive construction,allows easy practical realization of the method of the invention usingstructural components available on the market.

The timing pulses can be adjusted and adapted to applicable operatingconditions. The clock generator always assures correctly timed operationof the individual components of the device that are affected by it. Thusthe use of a microprocessor is proved to be especially favorable,especially since a microprocessor is both commercially available andinexpensive and operates in an energy-saving way. The microprocessor canthen control the entire course of operation of the device.

One embodiment enables temporary, incrementally renewable storage inmemory of information corresponding to the course over time of theradiation intensity.

The integration intervals can be shifted under random control to furthersuppress error.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described below in further detail in terms ofexemplary embodiments shown in the drawings. Shown are:

FIG. 1, in a schematic plan view, a weathering testing device with adevice operating by the method of the invention;

FIG. 2, in a schematic block circuit diagram, circuitry details of thedevice for performing the method of the invention; and

FIGS. 3A-3D, graphs for further exemplary explanation of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1, a stationary radiation device 10 constructed in one ormultiple parts, for generating UV and global radiation, is located in aclosed housing G of a weathering testing device. The radiation device 10is surrounded by stationary radiation-disrupting obstacles presented theequipment, such as absorber baffles 12, rain bars 14, and othermechanical parts of the equipment. A circular path of motion 16 extendsaround the radiation device 10, the latter being positioned centrally,for instance. Samples 18 to be examined, three of which are shown asexamples, are guided in operation along the path of motion 16 around theradiation device 10 and acted upon by the radiation of the radiationdevice 10.

The course over time of the radiation intensity at the location of thesample to be examined is detected with at least one sensor 20 thatreacts to the radiation of the radiation device 10. This sensor islikewise moved along the path of motion 16 together with the samples andin the present case is disposed offset in the circumferential directionfrom the samples 18. It could also be offset in height relative to thesamples 18, instead, without any circumferential offset.

The stationary mechanical parts that intersect the beam path from theradiation device 10 to the samples 18 and also to the sensor 20 lead tounavoidable measurement errors. These errors can have extremely adverseeffects, especially whenever the sensor 10 makes only brief snapshots ofthe radiation intensity at relatively long time intervals. In that caseit can happen that repeatedly, the sensor 20 is in operation only in theradiation disrupting range. Mains disruptions can also repeatedly haveadverse effects. To overcome these disadvantages, the device forperforming the method is constructed as shown in FIG. 2.

In FIG. 2, as the sensor 20, a receiving diode 22 that is sensitive tothe radiation of the radiation device 10 and is moved along the path ofmotion 16 is connected on the output side, via an amplifier 24, to aclocked integrator 26, which in turn is connected to an analog/digitalconverter 28. The output of the analog/digital converter is coupled toan averaging addition element 30, which is connected to a memory element32. The contents of the memory can be shown on a display device 34. Amicroprocessor 36 controls the individual components of the device andcan, as in the present case, be linked with a random generator 38.

The microprocessor 36, also functioning as a clock generator, generatesa first adjustable timing code with relative short successive codeintervals a, which in the example of FIG. 3 have a length of 1 second(or 0.5 seconds). It also generates even shorter integration intervalsc, which in FIG. 3 have a length of 0.4 seconds, as an example. In FIG.3, as an example, two integration intervals c of equal length per codeinterval a are generated, which are distributed without overlap and withmutual chronological spacing over the code interval a; in the example ofFIG. 3, they end in the code interval a at 0.5 and 1.0 seconds.

During each integration interval c, the integrator 26 assures an analogintegration of the measurement signal from the receiving diode 22. Themeasurement value of the integrator 26 that is available at the end ofeach integration interval c is digitized by the analog/digital converter28. A train of the digitized values is shown schematically in FIG. 3B.

The microprocessor 36 also generates a second adjustable timing codewith comparatively longer successive code intervals b, which in FIG. 3Chave a length of 60 seconds, as an example. During each code interval b,the digitized measurement values belonging together from a plurality ofsuccessive code intervals a are arithmetically added up and averaged bythe addition element 30. The arithmetical addition of the digitizedvalues during the code interval b is shown schematically in FIG. 3C,represented symbolically by a stairstep curve.

The measurement values output at the end of each of the code intervals bby the addition element 30 are stored in the memory element 34 inchronologically correct order and can thus be shown on the displaydevice with correct timing. A limited number of the most recentlyoccurring measurement values from the addition element 30 are shown inFIG. 3D and are stored in the memory element 32 at any given time. Tothat end, the memory element 32 is embodied as a shift register, forexample, through which the measurement values run.

With the random generator, the position of the integration intervals cwithin the code intervals can be shifted under random control.

The device can be modified in manifold ways within the scope of theinvention. For instance, the code intervals a, b of the timing codes andthe number and position of the integration intervals c within the codeintervals and the number of measurement values stored simultaneously inthe memory element 32 at a given time can be adapted to the prevailingrequirements at the time. The detailed technical layout of the equipmentcan also be modified in manifold ways.

What is claimed is:
 1. A method for determining the course over time ofthe radiation intensity at the location of at least one sample to beexamined, which moves in an enclosed sample chamber of a weatheringtesting device over a circular path of motion about a stationaryradiation device for generating UV and global radiation, having at leastone sensor detecting the instantaneous radiation intensity of theradiation device, which sensor, together with the at least one sampleand offset from it relative to the radiation device, moves substantiallyalong the path of motion, and an electrical measurement signalcorresponding to the instantaneous radiation intensity is derived by thesensor at intervals over time, characterized in that the measurementsignal is integrated in analog fashion in accordance with a first,adjustable timing code with relatively short code intervals at leastonce in each of these short code intervals via a certain integrationinterval of adjustable chronological length; that the thus-obtainedanalog-integrated measurement values of each short code interval aredigitized; that the digitized measurement values of a plurality ofsuccessive code intervals of the first timing code are arithmeticallyadded and averaged in accordance with a second, adjustable timing codewith comparatively longer code intervals, in each of these longer codeintervals; and that the thus-obtained arithmetically added, averagedmeasurement values are stored in memory digitally in such a manner thatthey can be chronologically ordered and can be called up.
 2. The methodof claim 1, characterized in that the arithmetically added, averagedmeasurement values are stored in memory such that they can be called upover an adjustable longer time period.
 3. The method of claim 1,characterized in that the integration intervals are chronologicallyshifted within successive code intervals of the first timing code. 4.The method of claim 3, characterized in that the integration intervalsare shifted chronologically irregularly, as if randomly controlled,within successive code intervals of the first timing code.
 5. The methodof claim 1, characterized in that the first timing code has constantcode intervals of approximately 500 milliseconds; that per codeinterval, one integration interval with a length of approximately 200 toapproximately 500 milliseconds is used; and that the second timing codehas constant code intervals of approximately 60 seconds.
 6. The methodof claim 1, characterized in that the integration intervals of the firsttiming code each end at the end of respective constant code intervals.7. The method of claim 1, characterized in that the integrationintervals of the first timing code each begin at the beginning ofrespective constant code intervals.
 8. The method of one of claim 1,characterized in that at least two integration intervals that do notoverlap chronologically are used per code interval of the first timingcode.
 9. The method of claim 8, characterized in that the at least twointegration intervals are of equal length.
 10. The method of claim 8,characterized in that the at least two integration intervals are ofdifferent lengths, and that their total length is the same in all thecode intervals of the first timing code.
 11. The method of claim 1,characterized in that in addition to the radiation intensity, othermeasurement variables are detected in accordance with theradiation-dependent measurement signal and processed further.
 12. Adevice for performing the method of claim 1, having at least one sensordetecting the instantaneous radiation intensity of the central radiationdevice, which sensor moves together with the at least one measurementsample and offset from it relative to the radiation device, over thecircular path of motion, and an electrical measurement signalcorresponding to the instantaneous radiation intensity as derived by thesensor, characterized in that connected to the output of the sensor (20,22) is a clocked analog integrator (26), which in analog fashionintegrates the measurement signal, in accordance with a first,adjustable timing code with relatively short code intervals (a) at leastonce in each of these short code intervals, via a certain integrationinterval (c) of adjustable chronological length; that connected to theoutput of the integrator (26) is an analog/digital converter (28), whichdigitizes the analog-integrated measurement values of the integratoreach at the end of the individual integration intervals (c); thatconnected to the output of the analog/digital converter (28) is anaveraging addition element (30), which arithmetically adds and averagesthe digitized measurement values of a plurality successive codeintervals (a) of the first timing code in accordance with a second,adjustable timing code with comparatively longer code intervals (b) ineach of these longer code intervals; and that connected to the output ofthe addition element (30) is a memory element (32) for storingsuccessive, arithmetically added, averaged measurement samples in memoryin a manner that can be chronologically ordered and called up.
 13. Thedevice of claim 12, characterized in that the integrator (26), theanalog/digital converter (28), and the addition element (30) areconnected to at least one adjustable clock generator (36).
 14. Thedevice of claim 12, characterized by a microprocessor (36) thatgenerates both the first and second timing codes and the integrationintervals and controls the individual elements of the device.
 15. Thedevice of claims 12, characterized in that the memory element (32) isembodied as a shift register.
 16. The device of claim 12, characterizedby a random generator (38), connected to a clock generator ormicroprocessor (36), for randomly controlled shifting of the integrationintervals.